Catalyst for the manufacture of acrylonitrile

ABSTRACT

A catalyst composition comprising a complex of catalytic oxides of iron, bismuth, molybdenum, cobalt, cerium, antimony, at least one of nickel or magnesium, and at least one of lithium, sodium, potassium, rubidium, or thallium, and characterized by the following empirical formula: 
     A a B b C c Fe d Bi e Co f Ce g Sb h Mo m O x   
     wherein  
     A is at least one of Cr, P, Sn, Te, B, Ge, Zn, In, Mn, Ca, W, or mixtures thereof  
     B is at least one of Li, Na, K, Rb, Cs, Tl, or mixtures thereof  
     C is least one of Ni, Mg or mixtures thereof  
     a is 0 to 4.0  
     b is 0.01 to 1.5  
     c is 1.0 to 10.0  
     d is 0.1 to 5.0  
     e is 0.1 to 2.0  
     f is 0.1 to 10.0  
     g is 0.1 to 2.0  
     h is 0.1 to 2.0  
     m is 12.0 to 18.0 and  
     x is a number determined by the valence requirements of the other elements present.  
     The catalyst is useful in processes for the ammoxidation of an olefin selected from the group consisting of propylene, isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile and mixtures thereof, respectively.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an improved catalyst for use inthe ammoxidation of an unsaturated hydrocarbon to the correspondingunsaturated nitrile. In particular, the present invention is directed toan improved process and catalyst for the ammoxidation of propyleneand/or isobutylene to acrylonitrile and/or methacrylonitrile,respectively. More specifically, the invention relates to a novel andimproved ammoxidation catalyst comprising a complex of catalytic oxidesof iron, bismuth, molybdenum, cobalt, cerium, antimony, at least one ofnickel or magnesium, and at least one of lithium, sodium, potassium,rubidium, or thallium.

[0003] 2. Description of the Prior Art

[0004] There are many patents related to the production of acrylonitrileby the use of bismuth-molybdenum-iron fluidized bed catalysts. Inparticular, Great Britain Patent 1436475; U.S. Pat. Nos. 4,766,232;4,377,534; 4,040,978; 4,168,246; 5,223,469 and 4,863,891 are eachdirected to bismuth-molybdenum-iron catalysts which may be promoted withthe Group II elements to produce acrylonitrile. In addition, U.S. Pat.No. 4,190,608 discloses similarly promoted bismuth-molybdenum-ironcatalyst for oxidation of olefins. U.S. Pat. Nos. 5,093,299 and5,212,137 are directed to bismuth-molybdenum promoted catalysts whichshow high yields of acrylonitrile.

[0005] Catalysts containing oxides of iron, bismuth and molybdenum,promoted with suitable elements, as described in the aforementionedpatents have long been used for the conversion of propylene at elevatedtemperatures in the presence of ammonia and oxygen (usually in the formof air) to manufacture acrylonitrile.

[0006] An object of the instant invention is a novel catalyst comprisinga unique combination of promoters offering better performance in thecatalytic ammoxidation of propylene, isobutylene or mixtures thereof, toacrylonitrile, methacrylonitrile and mixtures thereof, respectively.

SUMMARY OF THE INVENTION

[0007] The present invention is directed to an improved catalyst andprocess for the ammoxidation of propylene and/or isobutylene toacrylonitrile and/or methacrylonitrile, respectively. The presentinvention is a novel catalyst characterized by the following empiricalformula:

A_(a)B_(b)C_(c)Fe_(d)Bi_(e)Co_(f)Ce_(g)Sb_(h)Mo_(m)O_(x)

[0008] wherein

[0009] A is at least one of Cr, P, Sn, Te, B, Ge, Zn, In, Mn, Ca, W, ormixtures thereof

[0010] B is at least one of Li, Na, K, Rb, Cs, Tl, or mixtures thereof

[0011] C is least one of Ni, Mg or mixtures thereof

[0012] a is 0 to 4.0

[0013] b is 0.01 to 1.5

[0014] c is 1.0 to 10.0

[0015] d is 0.1 to 5.0

[0016] e is 0.1 to 2.0

[0017] f is 0.1 to 10.0

[0018] g is 0.1 to 2.0

[0019] h is 0.1 to 2.0

[0020] m is 12.0 to 18.0 and

[0021] x is a number determined by the valence requirements of the otherelements present.

[0022] The present invention is also directed to a process for theconversion of an olefin selected from the group consisting of propylene,isobutylene or mixtures thereof, to acrylonitrile, methacrylonitrile andmixtures thereof, respectively, by reacting in the vapor phase at anelevated temperature and pressure said olefin with a molecular oxygencontaining gas and ammonia in the presence of an mixed metal oxidecatalyst, wherein the catalyst has the empirical formula shown above.

DETAILED DESCRIPTION OF THE INVENTION

[0023] The present invention is directed to an ammoxidation catalystcomprising a complex of catalytic oxides of iron, bismuth, molybdenum,cobalt, cerium, antimony, at least one of nickel or magnesium, and atleast one of lithium, sodium, potassium, rubidium, or thallium,characterized by the following empirical formula:

A_(a)B_(b)C_(c)Fe_(d)Bi_(e)Co_(f)Ce_(g)Sb_(h)Mo_(m)O_(x)

[0024] wherein

[0025] A is at least one of Cr, P, Sn, Te, B, Ge, Zn, In, Mn, Ca, W, ormixtures thereof

[0026] B is at least one of Li, Na, K, Rb, Cs, Tl, or mixtures thereof

[0027] C is least one of Ni, Mg or mixtures thereof

[0028] a is 0 to 4.0

[0029] b is 0.01 to 1.5

[0030] c is 1.0 to 10.0

[0031] d is 0.1 to 5.0

[0032] e is 0.1 to 2.0

[0033] f is 0.1 to 10.0

[0034] g is 0.1 to 2.0

[0035] h is 0.1 to 2.0

[0036] m is 12.0 to 18.0 and

[0037] x is a number determined by the valence requirements of the otherelements present.

[0038] The “A” component is an optional element in the above catalyst.If “A” is present, “A” is preferably selected from the group comprisingCr, P, Ge, Ca or mixtures thereof. In a preferred embodiment of thepresent invention, “B” is selected to be one or more of Li, Na, K, Cs,or mixtures thereof, especially preferred being Li, Cs, K or mixturesthereof. In a preferred embodiment of the present invention, “C” is amixture of Ni and Mg, i.e. the catalyst contains both Ni and Mg.

[0039] In other preferred embodiments of the present invention, “a” mayindependently range from about 0.1 to 4.0, especially preferred beingabout 0.1 to 3.0; “b” may independently range from about 0.05 to 1.2,especially preferred being about 0.1 to 1.0; “c” may independently rangefrom about 2.0 to 9.0, especially preferred being about 2.0 to 8.0; “d”may independently range from about 0.5 to 5.0, especially preferredbeing about 1.0 to 4.0; “e” may independently range from about 0.1 to1.5, especially preferred being about 0.1 to 1.0, “f” may independentlyrange from about 1.0 to 7.0, especially preferred being about 1.0 to1.5; “g” may independently range from about 0.3 to 1.5, especiallypreferred being about 0.3 to 1.2; “h” may independently range from about0.3 to 1.5, especially preferred being about 0.3 to 1.2; and “m” mayindependently range from about 13.0 to 16.0.

[0040] The catalyst of the present invention can be used eithersupported or unsupported. Preferably the catalyst is supported onsilica, alumina zirconium, titania, or mixtures thereof, especiallypreferred as a catalyst support is silica. The amount of catalystsupport employed may vary. Typically the support comprises between about30 and 70 percent of total catalyst weight, more preferably about 50percent of total catalyst weight.

[0041] Examples of catalyst compositions of this invention include:

[0042] K₀ ₂Ni₃ ₀Mg₂ ₀Fe₂ ₀Bi₀ ₅Co₃ ₅Ce₁ ₀Sb₀ ₅Mo₁₃ ₆O_(x)+50 wt % SiO₂

[0043] K₀ ₂Ni₄ ₅Mg₁ ₅Fe₂ ₀Bi₀ ₅Ca₀ ₂Co₁ ₇Ce_(0.5)Sb_(0.5)Mo₁₃ ₆O_(x)+50wt % SiO₂

[0044] Cs_(0.1)K₀ ₁Mg₂ ₀Fe₂ ₀Bi₀ ₅Co₆ ₂Ce₀ ₅Sb₀ ₃Mo₁₃ ₆O_(x)+50 wt %SiO₂

[0045] Cs₀ ₁₅Ni₃ ₀Mg₂ ₅Fe₁ ₅Bi₀ ₃Co₃ ₀Ce₀ ₅Sb₀ ₅W₀ ₂Mo_(13 0 O) _(x)+50wt % SiO₂

[0046] Cs₀ ₁₅Ni_(2.5)Mg₂ ₅Fe₁ ₅Bi₀ ₃Li₁ ₀ ₂Co₂ ₈Ce₁ ₀Sb₀ ₅Mo₁ ₃₀O_(x)+50 wt % SiO₂

[0047] Cs₀ ₁K₀ ₁Ni₅ ₀Mg₂ ₅Fe₁ ₅Bi₀ ₃P₀ ₂Co₁ ₀Ce_(0.5)Sb₀ ₅Mo₁ ₃ ₀O_(x)+50 wt % SiO₂

[0048] Cs₀ ₁K₀ ₁Ni₄ ₀Mg₂ ₀Fe₂ ₀Bi₀ ₅Co₂ ₂Ce₀ ₃Cr₀ ₂Sb₀ ₃Mo₁₃ ₆O_(x)+50wt % SiO₂

[0049] The catalysts of the present invention may be prepared by any ofthe numerous methods of catalyst preparation which are known to those ofskill in the art. For example, the catalyst may be manufactured byco-precipitating the various ingredients. The co-precipitating mass maythen be dried and ground to an appropriate size. Alternatively, theco-precipitated material may be slurried and spray dried in accordancewith conventional techniques. The catalyst may be extruded as pellets orformed into spears in oil as is well known in the art. Alternatively,the catalyst components may be mixed with a support in the form of theslurry followed by drying or they may be impregnated on silica or othersupports. For particular procedures for manufacturing the catalyst, seeU.S. Pat. Nos. 5,093,299; 4,863,891 and 4,766,232 assigned to theAssignee of the present invention, herein incorporated by reference.

[0050] The “A” component of the catalyst (i.e. at least one of Cr, P,Sn, Te, B, Ge, Zn, In, Mn, Ca, W, or mixtures thereof) may be derivedfrom any suitable source. For example, cobalt, nickel and magnesium maybe introduced into the catalyst using nitrate salts. Additionally,magnesium may be introduced into the catalyst as an insoluble carbonateor hydroxide which upon heat treating results in an oxide. Phosphorusmay be introduced in the catalyst as an alkaline metal salt or alkalineearth metal salt or the ammonium salt but is preferably introduced asphosphoric acid. Calcium may be added via pre-formation of calciummolybdate or by impregnation or by other means known in the art.

[0051] Typically, the “B” component of the catalyst (i.e. at least oneof Li, Na, K, Rb, Cs, Tl, or mixtures thereof) may be introduced intothe catalyst as an oxide or as a salt which upon calcination will yieldthe oxide. Preferably, salts such as nitrates which are readilyavailable and easily soluble are used as the means of incorporating theA element into the catalyst.

[0052] Bismuth may be introduced into the catalyst as an oxide or as asalt which upon calcination will yield the oxide. The water solublesalts which are easily dispersed but form stable oxides upon heattreating are preferred. An especially preferred source for introducingbismuth is bismuth nitrate which has been dissolved in a solution ofnitric acid.

[0053] To introduce the iron component into the catalyst, one may useany compound of iron which, upon calcination will result in the oxides.As with the other elements, water soluble salts are preferred for theease with which they may be uniformly dispersed within the catalyst.Most preferred is ferric nitrate.

[0054] The molybdenum component of the catalyst may be introduced fromany molybdenum oxide such as dioxide, trioxide, pentoxide or heptaoxide.However, it is preferred that a hydrolizable or decomposable molybdenumsalt be utilized as the source of the molybdenum. The most preferredstarting material is ammonium heptamolybdate.

[0055] The catalysts are prepared by mixing an aqueous solution ofammonium heptamolybdate with a silica sol to which a slurry containingthe compounds, preferably nitrates of the other elements, is added. Thesolid material is then dried, denitrified and calcined. Preferably thecatalyst is spray-dried at a temperature of between 110° C. to 350° C.,preferably 110° C. to 250° C., most preferably 110° C. to 180° C. Thedenitrification temperature may range from 100° C. to 500° C.,preferably 250° C. to 450° C. Finally, calcination takes place at atemperature of between 300° C. to 700° C., preferably between 350° C. to650° C.

[0056] The catalysts of the instant invention are useful in ammoxidationprocesses for the conversion of an olefin selected from the groupconsisting of propylene, isobutylene or mixtures thereof, toacrylonitrile, methacrylonitrile and mixtures thereof, respectively, byreacting in the vapor phase at an elevated temperature and pressure saidolefin with a molecular oxygen containing gas and ammonia in thepresence of the catalyst.

[0057] Preferably, the ammoxidation reaction is performed in a fluid bedreactor although other types of reactors such as transport line reactorsare envisioned. Fluid bed reactors, for the manufacture of acrylonitrileare well known in the prior art. For example, the reactor design setforth in U.S. Pat. No. 3,230,246, herein incorporated by reference, issuitable.

[0058] Conditions for the ammoxidation reaction to occur are also wellknown in the prior art as evidenced by U.S. Pat. Nos. 5,093,299;4,863,891; 4,767,878 and 4,503,001; herein incorporated by reference.Typically, the ammoxidation process is performed by contacting propyleneor isobutylene in the presence of ammonia and oxygen with a fluid bedcatalyst at an elevated temperature to produce the acrylonitrile ormethacrylonitrile. Any source of oxygen may be employed. For economicreasons, however, it is preferred to use air. The typical molar ratio ofthe oxygen to olefin in the feed should range from 0.5:1 to 4:1,preferably from 1:1 to 3:1. The molar ratio of ammonia to olefin in thefeed in the reaction may vary from between 0.5:1 to 5:1. There is reallyno upper limit for the ammonia-olefin ratio, but there is generally noreason to exceed a ratio of 5:1 for economic reasons. Preferred feedratios for the catalyst of the instant invention for the production ofacrylonitrile are an ammonia to propylene ratio in the range of 0.9:1 to1.3:1, and air to propylene ratio of 8.0:1 to 12.0:1.

[0059] The reaction is carried out at a temperature of between theranges of about 260° to 600° C., preferred ranges being 310° to 500° C.,especially preferred being 350° to 480° C. The contact time, althoughnot critical, is generally in the range of 0.1 to 50 seconds, withpreference being to a contact time of 1 to 15 seconds.

[0060] The products of reaction may be recovered and purified by any ofthe methods known to those skilled in the art. One such method involvesscrubbing the effluent gases from the reactor with cold water or anappropriate solvent to remove the products of the reaction and thenpurifying the reaction product by distillation.

[0061] The primary utility of the catalyst of the instant invention isfor the ammoxidation of propylene to acrylonitrile. However, the instantcatalyst may also be used for the oxidation of propylene to acrylicacid. Such processes are typically two stage processes, whereinpropylene is converted in the presence of a catalyst to primarilyacrolein in the first stage and the acrolein is converted in thepresence of a catalyst to primarily acrylic acid in the second stage.The catalyst described herein is suitable for use in one or both stages.

Specific Embodiments

[0062] In order to illustrate the instant invention the followingexamples are provided below for illustrative purposes only.

EXAMPLE

[0063] A catalyst of the formula K₀ ₂Ni₃ ₀Mg₂ ₀Fe₂ ₀Bi₀ ₅Co₃ ₅Ce₁ ₀Sb₀₅Mo₁₃ ₆O_(x)+50 wt % SiO₂ was prepared as follows: 196.49 g of ammoniumheptamolybdate (AHM) were dissolved in 400 ml water. 625 g of silica solcontaining 40% by weight SiO₂ was added to the AHM solution followed by5.96 g of Sb₂O₃. Finally, a mixture of melted metal nitrates was addedcontaining: 66.12 g Fe(NO3)₃.9H₂O, 71.39 g Ni(NO₃)₂.6H₂O, 83.36 gCo(NO₃)₂.6H₂O, 41.96 g Mg(NO₃)₂.6H₂O, 19.85 g Bi(NO₃)₃.5H₂O, 1.66 gKNO₃, and 89.73 g of Ce(NH₄)₂(NO₃)₆.6H₂O as a 50% solution. Theresultant slurry was blended and then spray dried to give 479 gcatalyst. The catalyst was heat treated 3 hours at 290° C. followed by 3hours at 425 ° C. and finally 3 hours at 600° C. to give a finishedcatalyst.

Comparative Examples A through G

[0064] Using the preparation described above, several other catalystwere similarly prepared which omitted one or more of cobalt, cerium orantimony from the preparation. The composition of these catalysts are asset forth below in Table 1.

[0065] In order to identify the illustrate the performance of theclaimed cobalt, cerium and antimony promoted catalysts to similarcatalysts omitting one or more of these elements, all catalysts wereevaluated under similar reaction conditions. A feed containing a mixtureof 1C₃ ⁼/1.2NH₃/9.5 Air was fed over the following catalysts in an 1″diameter reactor approximately at 430° C., 10 psig and 0.09 wwh. Theyield of acrylonitrile was collected and measured. TABLE 1 CatalystComposition Total C₃ ⁼ Conv. to Examples (all compositions are + 50 wt %SiO₂) Conv. AN ExampleK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5)Co_(3.5)Ce_(1.0)Sb_(0.5)Mo_(13.6)O_(x)98.0% 79.8% Comp A K_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5) —Ce_(1.0)Sb_(0.5)Mo_(13.6)O_(x) 71.7% 56.9% Comp BK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5)Co_(3.5) — Sb_(0.5)Mo_(13.6)O_(x)80.4% 64.1% Comp CK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5)Co_(3.5)Ce_(1.0) — Mo_(13.6)O_(x)97.1% 76.2% Comp D K_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5)Co_(3.5) — —Mo_(13.6)O_(x) 85.7% 67.3% Comp EK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5) — — Sb_(0.5)Mo_(13.6)O_(x) 79.6%64.2% ExampleK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5)Co_(3.5)Ce_(1.0)Sb_(0.5)Mo_(13.6)O_(x)98.0% 33 79.8% Comp F K_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5) — Ce_(1.0)— Mo_(13.6)O_(x) 85.1% 66.8% Comp GK_(0.2)Ni_(3.0)Mg_(2.0)Fe_(2.0)Bi_(0.5) — — — Mo_(13.6)O_(x) 79.7% 60.4%

[0066] The catalyst composition of the instant invention is unique inthat it contains three promoting elements, cobalt, cerium and antimony,not previously utilized in combination in a single ammoxidation catalystformulation. As illustrated in Table 1, for the ammoxidation ofpropylene to acrylonitrile, a catalyst of the instant invention hasexhibited better performance than prior art catalyst containing none,one or two of these elements. More specifically, a catalyst containingcobalt, cerium and antimony showed higher overall conversion and higherconversions to acrylonitrile when propylene was ammoxidized over suchcatalyst at elevated temperatures in the presence of ammonia and air.

[0067] While the present invention has been described in conjunctionwith the specific embodiment set forth above, it is evident that manyalternatives, modifications, and variations will be apparent to thoseskilled in the art in light of the foregoing description. Accordingly,it is intended to embrace all such alternatives, modifications andvariations as fall within the spirit and broad scope of the appendedclaims.

The claimed invention is:
 1. A catalyst composition comprising a complexof catalytic oxides of iron, bismuth, molybdenum, cobalt, cerium,antimony, at least one of nickel or magnesium, and at least one oflithium, sodium, potassium, rubidium, or thallium, and having thefollowing empirical formula:A_(a)B_(b)C_(c)Fe_(d)Bi_(e)Co_(f)Ce_(g)Sb_(h)Mo_(m)O_(x) wherein A is atleast one of Cr, P, Sn, Te, B, Ge, Zn, In, Mn, Ca, W, or mixturesthereof, B is at least one of Li, Na, K, Rb, Cs, Tl, or mixturesthereof, C is least one of Ni, Mg or mixtures thereof, a is 0 to 4.0, bis 0.01 to 1.5, c is 1.0 to 10.0, d is 0.1 to 5.0, e is 1.0 to 2.0, f is0.1 to 10.0, g is 0.1 to 2.0, h is 0.1 to 2.0, m is 12.0 to 18.0, and xis a number determined by the valence requirements of the other elementspresent.
 2. The catalyst of claim 1 supported on an inert supportselected from the group consisting of silica, alumina, zirconia, titaniaand mixtures thereof.
 3. The catalyst of claim 1, wherein B is selectedfrom the group consisting of Na, Li, K, Cs or mixtures thereof.
 4. Thecatalyst of claim 1 wherein C is a mixture of Ni and Mg.
 5. A processfor the conversion of an olefin selected from the group consisting ofpropylene, isobutylene or mixtures thereof, to acrylonitrile,methacrylonitrile and mixtures. thereof, respectively, by reacting inthe vapor phase at an elevated temperature and pressure said olefin witha molecular oxygen containing gas and ammonia in the presence of anoxide catalyst, wherein the catalyst has the following empiricalformula: A_(a)B_(b)C_(c)Fe_(d)Bi_(e)Co_(f)Ce_(g)Sb_(h)Mo_(m)O_(x)wherein A is at least one of Cr, P, Sn, Te, B, Ge, Zn, In, Mn, Ca, W, ormixtures thereof B is at least one of Li, Na, K, Rb, Cs, Tl, or mixturesthereof C is at least one of Ni, Mg or mixtures thereof a is 0 to 4.0 bis 0.01 to 1.5 c is 1.0 to 10.0 d is 0.1 to 5.0 e is 0.1 to 2.0 f is 0.1to 10.0 g is 0.1 to 2.0 h is 0.1 to 2.0 m is 12.0 to 18.0 and x is anumber determined by the valence requirements of the other elementspresent.
 6. The process of claim 5, wherein the catalyst is supported onan inert support selected from the group consisting of silica, alumina,zirconia, titania and mixtures thereof.
 7. The process of claim 5,wherein B is selected from the group consisting of Na, Li, K, Cs ormixtures thereof.
 8. The process of claim 5, wherein C is a mixture ofNi and Mg.